Gas laser and method

ABSTRACT

A gas laser includes a glass bulb, end-face end pieces of sintered glass, a laser capillary, and mirror mounts fused to one another by glass solder. A method is also disclosed for manufacturing such gas laser, which is particularly suited for lasers of high light yield with high thermal stability.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a gas laser having adischarge vessel within which is mounted a laser capillary.

2. Description of the Related Art

A gas laser is disclosed in German patent no. 25 06 707, andcorresponding U.S. Pat. No. 4,081,762. The disclosed gas laser includesa laser tube of glass closed with metal end caps, the temperaturecoefficient of the metal end caps generally being matched to that of thelaser tube. The metal end caps are less sensitive than the end sectionsof glass previously employed in gas lasers, and can accommodatemechanical stresses which arise, for example, from adjustment of thelaser mirror.

However, the metal end caps can also transmit stresses to the glass tubewith such intensity that breakage occurs at the junction. The metalcaps, moreover, are subject to asymmetrical deformations duringtemperature fluctuations as a consequence of bushings, as well as pumpstems which are connected to the metal caps. The asymmetricaldeformations lead to misadjustment of the laser beam and, thus, to aconsiderable energy loss. As consequence of any different coefficientsof expansion of the glass tube and the metal caps, changes in powerduring a warm-up period, which can last for up to fifteen minutes, areextremely disturbing for use in many applications.

The use of end pieces of sintered glass are known, for example, in flashbulbs.

SUMMARY OF THE INVENTION

An object of the present invention is to reduce temperature dependencyof laser output power and to avoid injurious stresses in a gas laser aswell as to increase yield in a set manufacturing process.

This and other objects are achieved in a gas laser having end pieces ofsintered glass connected to the glass bulb, or tube, of the dischargevessel. In accordance with the principles of the present invention, endpieces of sintered glass not only can be made vacuum-tight, but alsoexert very little stress on the tube during assembly and adjustment ofthe mirrors. Furthermore, sintered glass end pieces exhibit both asensitivity to mechanical stresses and guarantee a long-lasting, veryprecise fixing of the laser capillary and the mirror mounts.

Particular advantages are realized in an embodiment of the present gaslaser in which the glass tube, the end piece and the capillary are allcomposed of the same type of glass. The end piece is again formed ofsintered glass. In this embodiment, the temperature coefficients matchone another exactly and the individual parts can be directly fused toone another.

An especially low sensitivity to temperature fluctuations and anextremely high precision of the mirror adjustment and thus resultingvery high yield of the laser emission are thereby provided. For thetypes of glass suitable for use in the present gas laser, meltingtemperatures of approximately 500° C. are used for joining theindividual parts. Given this low temperature, tempering of the presentdevice is superfluous when all parts of the laser are to be fused to oneanother in a single work step. Temperature-independence and beamprecision are noticeably better in the above described embodiment thanwhen even the best metal caps available are used.

A further improvement lies in the absence of a pump stem on the gaslaser by having at least one surface of the end pieces of sintered glassthat is fused vacuum-tight after assembly of the present device. Thisavoids slight asymmetries produced by a pump stem and the resultingpositional changes in the optical parts during temperature fluctuations.Thus, there is no longer power instabilities during the warm-up period.

The mirrors for the gas laser are in mounts advantageously composed ofthin-walled tubes with a partially thick-wall portion forming an annulargrove. The thin-walled tube can be inserted and fused into acorresponding bore in the end pieces without introduction of disturbingstresses. The thick-walled portions having the annular groove enable themirror to be adjusted in a known way. For fixing an exact position ofthe mirror, the thick-walled portion includes a step to a thin-walledend region, and a thin-wall tube is inserted into this end region andsoldered thereon so that the thin-walled tube lies against the step.

A manufacturing method for the present invention provides an especiallyfavorable improvement when the laser is equipped with an aluminumcathode. The laser receives end pieces which are free of pump stems andwhich are composed of gas-permeable sintered glass. The end pieceswithout pump stems, the glass tube, the laser capillaries and the mountsare fused or soldered to one another in a single work step. Oxygen issubsequently admitted and the aluminum cathode disposed within the glasstube or bulb is oxidized thereby. The oxygen is suctioned off and alaser gas is admitted, and then at least one gas-permeable surface ofthe end piece is fused smooth and vacuumed-tight so that the tube orbulb is thereby rendered gas-tight.

The above method can be executed with particular advantage when aplurality of gas lasers are being formed in the same vacuum vessel.Sintered glass which is not tightly fused allows adequate gas to pass sothat the gas interchange occurs without difficulty. By a brief elevationin the temperature of the outer surface of the laser vessels, thesintered glass is ensured of having a vacuum-tight fused surface in asimple way. It is preferred in this method that the end pieces be of arelatively great thickness, at least compared to the outside diameter ofthe laser capillaries.

A further advantageous possibility for manufaturing gas lasers of thepresent invention is in utilizing glass solder for fastening the glassparts. In particular, a manufacturing method for gas lasers for havingan aluminum cathode disposed within a glass bulb includes, first, hardsoldering metal parts to one another, wherein the capillaries are fixedin position relative to the glass bulb. All parts of the bulb andcorresponding glass solder rings are stacked on top of one another in asoldering apparatus in their proper positions. Oxygen for oxidizing thealuminum cathode is blown in, or let in, and then suctioned off whilethe assembled parts are in the stacked position. A laser gas isthereafter admitted and the overall arrangement is heated to thesoldering temperature of the glass solder rings so that all glasssoldering is carried out in a single work step to produce a vacuum-tightgas laser.

The force of gravity of the parts of the laser vessel stacked on top ofone another is sufficient to guarantee a vacuum-tight soldering of thevessel parts. The described method enables short glass bulbs to be usedwhich hold the capillaries in a mechanically favorable position.Additional support for the capillaries can be omitted even when they areof a relatively great structural length. This is provided by thecapability of the glass solder to absorb mechanical stresses without arisk of breakage, the glass solder being able to absorb considerablyhigher stresses than other structural forms of laser tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is longitudinal cross section of a gas laser discharge vesselaccording to the principles of the present invention; and

FIG. 2 is an exploded view of a second embodiment of the present gaslaser.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 is shown a gas discharge vessel of a gas laser composed of aglass bulb 1 and of end pieces 2 and 3. The end pieces 2 and 3 are of asintered glass and include bores 4 and 5. The end pieces 2 and 3 areconnected to the glass bulb in a vacuum-tight fashion with glass solder.The glass solder absorbs stresses which arise as a consequence of slightdifferences in the coefficients of temperature expansion between the endpieces 2 and 3 and the glass bulb 1. Each of the end pieces 2 and 3include a widened outer region 6 of the bores 4 and 5 into which athin-walled part 9 of a mirror mount 10 is inserted. The thin-walledpart 9 lie against a step 11 at the end of the respective, widenedoutside regions 6. The thin-walled part 9 are connected to the endpieces 2 and 3 by glass-metal fusing. A particularly thick-walled part14 including an annular groove 12 is connected to the thin-walled part 9of the mount 10. Mirror adjustment is possible by deforming the mount 10in the region of the annular groove 12. An end region 13 of thepartially thick-walled part 10 is thin-walled and has a relatively smalloutside diameter. The thin-walled part 9 is in the shape of a tube andis slipped onto the region 13 and hard soldered.

A laser capillary 8 is inserted into a widened portion 7 of the bore 4at one side and is soldered to the end piece 2 with glass solder. Allglass solder connections are carried out in a single soldering procedurewhen the required glass solder is introduced in the form of glass solderrings during essembly of the individual parts.

An advantageous embodiment of the invention includes the glass bulb 1,the end pieces 2 and 3, and the laser capillary 8 composed of the sametype of glass. In this embodiment, the use of glass solder is omittedand the individual parts are joined by glass fusing.

At least on the surface, the end pieces 2 and 3 are fused smooth to sucha degree that they close the laser bulb 1 vacuum-tight. For at least oneof the end pieces 2 or 3, this smooth fusing is delayed until thevarious glass parts have been soldered or fused to one another. Theouter surface of the at least one end piece 2 or 3 is therebyparticularly well suited for a final smooth-fusing since heat can beapplied externally in a simple way. For the type of glass coming intoconsideration here, a melting point of, for example, 500° C.accomplishes the smooth-fusing without difficulty and without risk afterthe mount 10 has been inserted. Thus, the metal-glass fusing to themount 10 is simultaneously accomplished.

Before smooth-fusing, the corresponding end piece 2 and/or 3 is soporous and gas-permeable that gas can be suctioned out of the bulb 1through the end piece 2 or 3 without difficulty and then can be let inagain. In this case, a manufacturing method is advantageously utilizablewherein a great plurality of laser bulbs is accomodated within acompartment (not shown) and is first exposed to an oxygen atmosphere foroxidizing the aluminum cathode in a standard way. The oxygen is thenpumped off following the desired oxidation, and the laser gas is thenadmitted. Finally, smooth-fusing of the end pieces 2 and 3 occurs in thelaser gas atmosphere. For this method, it is possible to manufacturelaser tubes of the described species which are free of pump stems. Suchlaser tubes are especially insensitive to temperature fluctuations sinceasymmetry of the end pieces is eliminated, the asymmetry being producedin the known laser tubes by the required pump stems.

Referring now to FIG. 2, an example of a gas laser of the presentinvention is shown in exploded view. A glass solder ring 15 and an endpiece 16 of sintered glass without a pump stem follow an end face of theglass bulb 1. Metal parts, namely a metal tube 18, a hard solder ring17, and a mount 10, and at another end a metal cap 19, a hard solderring 17, and a mount 10 are soldered to one another in advance. Onerespective glass solder ring 22 serves to fasten the mirror 20, themetal tube 18 and the metal cap 19 to the neighboring parts and tofasten the capillary 8 in the glass tube 1.

All parts of the laser tube are stacked on top of one another in theirproper positions in the preferred method, the parts being stacked in asoldering apparatus which is not shown. Glass soldering is then executedin one work step. The capillary 8 is thereby held in the desiredposition relative to the glass tube 1 by a clamp mechanism (not shown).

Oxygen for oxidizing an aluminum cathode 21 is blown in and then pumpedout and then the laser gas is admitted. The gas exchange required forthis occurs through residual gaps existing between the glass solderrings 15 and 22 and the adjacent parts. Subsequently, the arrangement isheated to a soldering temperature for the glass solder rings 15 and 22so that all glass soldering is carried out in a single work step. Thesoldering temperature is perferably about 500° C. Gravity adequatelypresses the parts against one another so that a vacuum-tight seal arisesfrom the glass soldering.

The structure of the present gas laser of the invention considerablyboosts effieciency due to the optimum adjustment of the mirrors, sincethe mirror adjustment does not subsequently change and since the highestdegree of insensitivity to temperature fluctuations is achieved.Simultaneously, a cost-beneficial manufacturing method for the presentlaser is provided, particularly allowing simultaneous fabrication of aplurality of lasers in one and the same vacuum furnace.

Although other modifications and changes may be suggested by thoseskilled in the art, it is the intention of the inventor to embody withinthe patent warranted hereon all changes and modifications as reasonablyand properly come within the scope of his contribution to the art.

I claim:
 1. A discharge vessel for a gas laser, comprising:avacuum-tight glass bulb having an outer wall; a laser capillary rigidlyconnected to said discharge vessel at a first end of said glass bulb; afirst optical part secured to a first mount, said first mount includinga bore extending coaxially with said laser capillary; an end piececlosing said glass bulb at one end, said end piece having a borecoaxially aligned with said laser capillary, said end piece being ofsintered glass having a low sensitivity to temperature fluctuations andbeing connected to said glass bulb in vacuum-tight fashion; a secondmount aligned with and positioned at an end of said capillary oppositeto said first mount and bearing a second optical part; and said firstmount comprising a thin walled part connected to said end piece, saidfirst optical part secured in said first mount being a mirror.
 2. Adischarge vessel at claimed in claim 1, wherein said glass bulb and saidend piece and said capillary are of the same type of glass.
 3. Adischarge vessel as claimed in claim 1, wherein at least one surface ofsaid end piece is fused vacuum-tight after assembly.
 4. A dischargevessel as claimed in claim 1, wherein said first mount is a thin-walledtube having a thick-walled portion forming an annular groove.
 5. Adischarge vessel as claimed in claim 4, wherein said thick-walledportion provides a diameter step to a thin-walled end region, andsaidthin-walled tube is slipped onto said thin-walled end region and issoldered on and pressure against said diameter step.
 6. A dischargevessel as claimed in claim 1, further comprising:glass solder connectingsaid end piece and said optical parts and said capillary to respectiveadjoining parts of said glass bulb; said glass bulb having an end regionat one end of reduced diameter, said end region being connected to saidcapillary by said glass solder; and said capillary projecting beyondsaid glass bulb.
 7. A discharge vessel as claimed in claim 1, furthercomprising:a second end piece vacuum-tightly closing a second end ofsaid glass bulb, said second end piece being of sintered glass andbearing said second mount.